Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, cause cancer and even induce death. These poisons are produced by a variety of fungi. In order to develop rational tools for limiting contamination, it is necessary to identify the fungi that cause the majority of aflatoxin contamination. Recently, over a hundred deaths occurred in Kenya due to aflatoxin contamination of corn. As part of our efforts to identify the most important agents causing aflatoxin contamination, we examined the fungi causing these deadly aflatoxin outbreaks. The S strain of A. flavus, a fungus common in Texas and Arizona, was found to be the primary causative agent. This is the most compelling data to date, suggesting fungal community composition and specifically incidence of the S strain is an important determinant of contamination. The results suggest that strategies aimed at the S strain of A. flavus may be most effective at reducing aflatoxin contamination.

Technical Abstract:
Aflatoxins, hepatotoxic human carcinogens produced by several Aspergillus species, have been associated with deadly maize in Kenya three times since 1981, but the fungi contaminating the maize with aflatoxins have not been characterized. Here we associate the S strain of Aspergillus flavus, not previously known in Africa, with lethal aflatoxicoses that took over 125 lives in 2004. This causal agent should be the target of long-term preventative measures both in East Africa and in other places where the S strain is common, such as North America.